The proposed research includes three objectives - (1) Provide the background physical environmental factors for the study of ecological changes due to the formation of a man-made lake in a tropical forest on the natural history of arboviruses, (2) To prepare mathematical models of the preflooding and post-flooding microclimate for use in quantification of any changes in the ecology of vector borne diseases, (3) Investigate the influence of the changing microclimate on the epidemiology of vector borne disease, and to offer a basis of predictability for similar hydroelectric dam projects that are being developed in tropical America. Investigations on these objectives are taking place on the projected Bayano River Hydroelectric Dam 70 Km east of Panama City which will form a lake of 300 Km2. A camp was established in the forest of a future island in the lake. Three years of base line information has been collected including the microclimate data, ecological studies on vectors and hosts, and virological investigations of arboviruses detected in the area. Plans call to continue studies during the formation and stabilization of the lake, and to develop models of the correlation of those ecological-entomological-virological data collected with the changes in the microclimate.